Ernst bbandus



E BRANDU S.

March 12,; 192-9.

KETH OD APPAHATUS FOR PREPARING HATERIALS AND APPLICATIONS THEREOF Filed Feb. 20, 1925 5 'lNvgN'roR l'rizwfbrandar Patented Mar. 12, 1929.

ERNST BRANDUS, OF BERLIN, GERMANY.

amino]: AND Arrlmarus ron ranramne MATERIALS AND APPLICATIONS Jrnmmor.

Application filed-February 20, 1925, Serial No. 19,501, and in Germany January 13, 1925-.-

M present invention is shown applied to elimlnating distortion efiects an telephone cables due to the magneticinduct1on of. neighboring high tension alternating our- 6 rent transmission lines. The 'disturbancesvnoted are of two kinds, the electrostatic or capacity effect, which results from-groundingthe cable sheaths, and the inductive electromagnetic effect.

For obviating the inductive disturbances, between adjacent power lines, the same means appear to sufiice, which are used for protection against reciprocal disturbances of difierent lines in a multiple telephone cable, 15 that is, the same means which permits the greatest possible degree of electromagnetic symmetry of the different conductors, su1table control apparatus, etc.

'Without such protection the pract1ce of 2 telephony in large cities, as it has developed with the transmission lines in contiguity to power lines, would hardly be possible. The protective means mentioned frequently are insuflicient especially in those cases in which 2 telephone cables necessarily extend for substantial distances inuclose proximity to h1gh tension or high current conductors, as, for instance, in the train announcing telephone lines for electrical railroads. Beside the disturbances in telephony, it is noted, switching operations in the power clrcuit induce tensions in the telephone cables, which may break through the insulation thereof and endanger not only the installations themselves, but human life as well.

motive force E induced by a high power line in a contiguous low power, such as a telephone line:

,some advantages. The screening comparison to its diameter D, The following formula defines the electro-' decreasing R. t

As regards the decrease of R, this can be accomplished by the addition of copper wires in parallel, lengthwise of the cable. The self-inductance L may be increased, for instance, by armoring the cable with iron.

In addition to increase of the denominator able operation results by. increasing L and of the above equation, decrease of the numerator, that is, of the mutualinductance M, renders possible the reduction of the induc-' tive disturbances. This effect is utilized where cables are armored with iron, or enclosed in iron tubes. In the case of cable conductors, the principle has, however, not been'heretofore utilized for affording protectlon a ainst exterior magnetic fields, probably or the reason that the execution ofv this process up to now has involved considerable technical and mechanical difficulties.

According to my present invention, I have devised a new method of protecting telephone conductors from the effect of magnetic fields, induced from ,the exterior, which effectively utilizes the magnetic screening action of a ferrorma'gnetic enclosure of ,the cable strands.

From g eral theoretical considerations, it wouldappe 1'' that this result can. be best accomplished ply enclosing the cable in thick iron armor. ven the use of iron tubes as employed for many purposes would offer efi'ect S of is small in that is,-the relation of the magnetic field strengths at the exterior and the interior of'sfich armor, is given by the formula: I

an 1ron armor whose thiclmess where {see 'Graetz 'Handbuch d. Elektri zitat' imd des Magnetismus, Vol. IV,'page 164; 1913) ,u is the permeability of the ferromagnetic medium. An iron tube of m. m. diameter and 3 m9 m. thickness would, assuming the initial 'ermeability to be but 100, accordingly pro uce a screening eflect 8'. equal to about4. In this case, the dele- 'terious inductive action, ,assumin the cable to be centrally disposed, would ereduce by about 75 per cent. v

As many years of experience has taught,

however, iron tubes lodged in the earth, particularly when traversed by induced currents, are subject to the oxidizing influence of moisture to suchhigh degree that they are not practically utilizable for cable installations. 7 a

It is, accordingly, an object to provide a material. which besides having the weather and moisture resisting qualities of the usual lead alloy of which telephone cable sheaths are made, possesses ferro-magnetic properties and is capable of being worked in the same manner aslead."

The combination, for instance, of hydraulic binding mate'rial, paper, etc. rendered ferro-magnetic and enclosing the cable strands, provides a moisture and weather resisting material of practically, unlimited durability, having those magnetic properties that are necessary for'the desired protection from induction. Conversely, the spread oi? the deleterious magnetic fields engendered by high power transmission lines lodged in theearth may be inhibited, by embedding them in term-magnetic concrete conduits.

According to pre'sent scientific knowledge,

only the elements of the iron group, v1z., iron, nickel, cobalt and Heuslers alloy- (cop:

, per, manganese and aluminum bronze) have been known to present para-magnetic properties of suilicient magnitude to be practically utilizable as term-magnetic materials. Other materials which in their pure state are dia-magnetic, for instance, aluminum lead or zinc, or only Weakly para-magnetic,

I p less than would correspond to the proportion as for instance; tin, may be rendered magnetiz'able to a degree by the addition of iron, in so far as they may be. capable of being alloyed with iron. Such alloys, however, are in general para-magnetic to a degree far of iron therein. Furthermore, there is only a very limited possibility ot'forming alloys with iron. I

My attempts to increase the number of term-magnetic materials have met with .the result that even metals not belonging to the iron group, nor constituting a Heusler a1- 10 have been rendered ferro-magnetic.

".l ese new- .ferro-magnetic materials of my invention retain all of the ty ical properties of the non-magnetic constituents thereof. According to my invention, the new term-magnetic material may be formed in a homogeneous mass having a given weak or strong ferro-magnetic permeabillty. Fur thermore', the same piece may be magnetic in whole-or only at selectedareas or volumes, at the interior or the exterior thereof.

In a preferred speeific application, the telephone cable sheath or armoris formed of a special substance or alloy which has substantially the same mechanical properties as the 'usual lead alloy sheath. having mechanical strength including the capability of being readily made by extrusion, and being possessing a permeability proportional to the percentage of iron thereln. The comminuted iron may be combined with a base material of concrete, paper pulp, vulcanite or bakelite, metal alloys as well as 'metalloids and combinations of the same and in general conductors, semi-conductors and insulators, the product in every case having substantially the mechanical or hysical pro erties of the base material with super-ad ed magnetic permeability imparted by the iron.

The combination of metallic constituents, however, that do not form alloys by ordinary methods, for instance, lead and iron used for making telephone cable sheaths,

according to my invention, presents special difliculties which Ihave overcome. According to my. method, the iron is comminuted as is the lead or other constituent and the elements are mixed and caused to coalesce by pressure, the ph sical characteristics and specific gravity of t e product depending on they magnitude of the pressure applied. The preferred mode of comminuting is by atomizing by a blast of air or steam applied toa stream of molten lead flowing from the hop-' per, thereby causing the metal to. solidify inthe form of an impalpablep'owder, similarly treating the iron, intimately mixing the powders to e ther and then extruding the mixed pow er through a'die by means of a 1 hydraulic press. 0 H

In the accompanying drawings in which I have diagrammatically exemplified my method, a paratus and product,

Fig. 1 sowsdiagrammatically apparatus i for making my novel product,

Fig. 2 is a cross-sectional View of a tele-,

phone cable, and

Fig. 3 shows a cross-section of a telephone cable installation.

In Fig. 1 I have shown diagrammaticall' y i an apparatus for making a telephone cable sheath or other pipe by extrusion. The hydraulic press element isiof conventional construction including --.a cylinder 10 within which the metal is confinedandsubjected by I power transmitted through plunger 11 from operating cylinder to compression present embodiment, the molten lead passes from a hopper 12 by gravity flow through a nozzle 13 in a thin stream 14. The hopper and the nozzle may be heated to keep the lead molten, asby electrical heating wire C. The stream is subjected to a blast of compressed air, gas or steam admitted through pipe 15 and has the effect of atomizing and cooling the metal and causing the atomized particles of lead to form a fine or impalpable powder which drops into the mixing chamber 16. The energy of the atomized medium is dissipated in a muliler or system of bafiies 25 and the file-energized medium escapes at outlet 26. Iron treated in a generally similar way is also admitted to the mixing chamber by similar apparatus (not shown) through inlet 17 and the particles are intimately intermixed by any appropriate mixing apparatus 18 and are delivered from the mixing chamber into the extrusion cylinder 10, to be forced under hydraulic pressure through die 19. i

The extruded product is a pipe or sheath having the mechanical characteristics of the usual lead pipe or sheath, that 'is, it is impervious to acids, moisture or weather and easily bendable, but possesses magnetic permeability proportional to the percentage of iron in the. product. 7

Referring to Fig. 2, I have shown a preferred application of the method set forth, to a generally conventional underground telephone cable. -A bundle 20 of telephone conductors, each individually insulated, is enclosed in a gutta percha enclosure 21 which is covered with a paper coating 22, the latter enclosed in my preferred sheath 23 of lead alloy and iron.

It will be seen that a high tension alternating current transmission line, contiguous.- to the telephone cable will have no inductive effect on the conducting wires 21, since the sheath by reason of its pure iron constituent,

acts as a magnetic shell intercepting mag netic flux and preventing the same from 1nterlinking with or producing induction effects on the telephone conductors.

'As shown by the foregoing formula, the

screening effectiveness increases inversely with the diameter of the protective sheath.-

Accordingly, it is preferable to dispose'the ferro-magnetic sheath as closely as possible to the strands to be protecteth In the preferred embodiment, the ing effect is enhanced by also rendering para-magnetic the concrete cable conduit 24 shown in Fig. 3. This result is accomplished by the simple expedient of mixing insulatwith the grout of which the conduit is made, a suitable percentage of finely divided soft iron particles.

It is preferable also to form the paper layer 22 as a magnetic screen. This may be accomplished by combining with the paper pulp of which the same is made, an appropriate proportion of fine particles of iron and thereby forming a homogeneous paper having an iron constituent. Alternatively, the paper may be rendered magnetic by impacting on the surface thereof, fine particles of iron powder which will coalesce with the surface thereof, and be intimately combined therewith.

By using a plurality of layers of ferromagnetic material alternating with nonferrous layers, the screening effect is in creased more than by the use of solid iron armors of equivalent iron content. Accordingly, the combination of a magnetic lead sheath within an' iron cement cable 'conduit is a satisfactory arrangement, af-

above apparatus and method, and many apparently widely difierent embodiments of this invention could be made without departing from the scope thereof, it. is intended that all matter containedin the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 1

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is l. '.ahe method of forming a telephone cable armor capable of excluding magnetic stray fields from the cable strands, which method consists in finely comminuting the lead alloy-for said-cable, intimately intermixing therewith V finely comminuted iron particles and molding said mixture under high pressure to vform. the cable.

5 2. A magnetic substance including substantially homogeneously associated lead and ironcombining the mechanical properties of lead with the magnetic properties of Signed'at New York city in the county'of New York and State of New York this 18th day of February, A. D. 1925.

ERNST B aAnnus. 

